The invention generally relates to a delivery apparatus for bone cement and, in particular, to a bone cement delivery device that uses a dispensing mechanism for quickly priming the delivery apparatus and delivering the bone cement.
The necessity to apply bone cement to a bone during surgical procedures, such as the attachment of a prosthesis or pathological fracture fixation, has been well known in the surgical community. With regard to the attachment of a prosthesis, the cement is packed into the bone and the prosthesis is then attached. The cement cures and a bond develops between the bone and the prosthesis. Traditionally, surgeons have packed the bone cement into the bone by hand. A disadvantage to that technique is that often a weak bond develops between the bone and the prosthesis. When packing the cement by hand the surgeon unknowingly applies insufficient pressure and the cement fails to properly penetrate the bone, thereby creating a weaker bond. Additional disadvantages of packing the cement by hand include excessive time consumption and often the quickly curing cement hardens before the surgeon has finished packing the cement.
Other uses of bone cement include repairing or mending bone fractures or shattered bone occurring from extreme trauma. Bone cement may also be used during cosmetic or dental surgery. Moreover, bone cement may be used as a drug delivery or release system, whereby the bone cement is mixed with antibiotics or other desired drugs and applied to a specific surgical site such that the drugs leach out and are delivered directly to the surgical site. Some bone cements are also designed to be absorbed by the body over time.
To overcome some of these disadvantages, delivery apparatuses have been developed to apply the cement to the bone. One such apparatus greatly resembles a common household caulking gun with a cartridge of caulk. This prior art apparatus has a pistol-shaped body which supports a cartridge of bone cement. The apparatus includes a ram actuated by a movable trigger for pushing the cement out of the cartridge and through a nozzle. A pull of the trigger advances a rod that also advances the ram. The prior art delivery apparatuses also provide structures for adjusting the dispensed quantity of cement per trigger pull. Traditionally this adjustment is accomplished by preventing the full actuation of the trigger with a mechanical stop. The resulting quantity of dispensed cement after the mechanical adjustment is often an imprecise calculation. Additionally, the apparatus delivers a discrete amount of cement per xe2x80x9ctoothxe2x80x9d of the ram.
The prior art dispensing apparatus have many disadvantages. First, to advance the ram during an initial loading of the cartridge of cement the trigger must be actuated repetitively. This is a very time consuming step during a complex orthopedic surgery. Additionally, a bone cement delivery apparatus must be sterilized prior to being admitted into an operating room. Often the compact design of the delivery apparatus"" cartridge dispensing mechanism or trigger assembly makes sterilization in a traditional autoclave unit difficult because the steam is unable to properly penetrate the components of the apparatus.
Currently, there is a need for a delivery apparatus for bone cement with a simple, yet effective design that allows surgeons to quickly prime the apparatus when loading a new cartridge of cement, non-discretely dispensing cement, and properly sterilizing the apparatus.
In one aspect of the present invention, a delivery apparatus for injecting cement from a cartridge, is provided having a cradle with an axial cavity extending therethrough for supporting the cartridge, a cartridge dispensing mechanism coupled to the cradle and defining a cylindrical bore therein, a button having threads and defining an axial bore, a keyed bore disposed in the button and being linearly aligned with the cylindrical bore, a threaded rod in threaded engagement with the axial bore of the button and extending into the axial cavity of the cradle wherein the button is moveable into and out of threaded engagement with the threaded rod, and a locking pin_slideably disposed in both the cylindrical bore and the keyed bore for being moved from a first position to a second position.
In another aspect of the present invention, a delivery apparatus for injecting cement from a cartridge is provided having a cradle with an axial cavity extending therethrough for supporting the cartridge, a cartridge dispensing mechanism coupled to the cradle and defining a cylindrical bore therein, a button having threads and defining an axial bore, a keyed bore disposed in the button and being linearly aligned with the cylindrical bore, a threaded rod in threaded engagement with the axial bore of the button and extending into the axial cavity of the cradle wherein the button is moveable into and out of threaded engagement with the threaded rod, a locking pin slideably disposed in both the cylindrical bore and the keyed bore for being moved from a first position to a second position, a first cleaning passageway defined by the cartridge delivery mechanism and extending from the exterior thereof to the threaded engagement of the rod, threads disposed in the axial bore and being spaced from the threaded rod to define a second cleaning passageway for convey a cleaning medium therethrough, a biasing device for biasing the threads of the axial bore into threaded engagement with the threaded rod, a limiting structure for limiting travel of the button and minimizing friction and pinching between the button and the threaded rod, and bushings slidably supporting the threaded rod.